1. Field of the Invention
The present invention relates to a process for preparing a multilayer ceramic capacitor and the multilayer ceramic capacitor, and in particular, to a process for preparing a multilayer ceramic capacitor and the multilayer ceramic capacitor, wherein a base-metal material is used for a conductor pattern.
2. Description of Related Art
In recent years, in response to growing demand for smaller size and larger capacity, efforts have been made so that an internal electrode layer as well as a dielectric layer in a multilayer ceramic capacitor can be a thinner film. For example, a well-known method is to form on a film a conductor pattern that turns into an internal electrode layer, employing physically thin film forming method such as sputtering and deposition, or chemically thin-film forming method such as electroless plating (for example, Japanese Patent Application Laid-Open No. 2000-243650). In addition, as an appropriate forming method for mass production, it is proposed to employ electroplating method, using such electrolytic solution as nickel (for example, Japanese Patent Application Laid-Open No. 2003-309037).
According to the above conventional methods, it is possible to easily make conductor patterns thinner. However, among these thin films, especially, in a plated film obtained through electroplating method, metal additives that are added during manufacturing process, for example, sulfur etc. hardly form solid solution with Ni and are precipitated disproportionately in grain boundary portions of Ni in the form of an intermetallic compound such as Ni3S2 having a melting point of 640° C.
In cofiring with dielectric material green sheets, the intermetallic compound having a low melting point is melted. Therefore, the molting point of a base-metal material that is a main component is lowered, making conductor patterns discontinuous during cofiring with dielectric layers.
According to the above methods, among thin film of conductor patterns, especially, in a plated film obtained through electroplating method, in cofiring with dielectric material green sheets, the melting point of a base-metal material that is a main component is lowered, making conductor patterns discontinuous during cofiring with a dielectric layers.
As above, once conductor patterns turn discontinuous, the effective area of internal electrode layers is smaller, resulting in the problem of not being able to obtain desired electrostatic capacitance of a multilayer ceramic capacitor.
Moreover, when the conductor paste of nickel metal powder is used as an internal electrode layer, there is a problem that conductor patterns turn discontinuous, like the above-mentioned plated film.